Should I lose weight?

Nourish - Article 05

Many people are told they need to lose weight without much consideration of the bigger picture. However, throughout the Onko programme, our dietitians will be on hand to assess your individual situation and guide you through what can often be perceived as a nutritional minefield.

A person may be overweight but might have lost a lot of weight and muscle unintentionally – in this case, losing weight isn’t a good thing and the aim should be to increase oral intake. Equally, if you’re prone to ‘dieting’ or have a poor relationship with food, a better approach is to aim to eat healthier and get fitter without a linear focus on dieting or losing weight.

That being said, obesity can increase the risk of many chronic illnesses, including cancer, so if you’re at risk, dieting may be a factor your dietician will ask you to consider when approaching cancer treatment.

What’s the problem with obesity?

Obesity is a condition in which a person has too much body fat. It can be particularly problematic if your fat sits mostly around your middle, surrounding your internal organs and liver (visceral fat). While a little abdominal fat is to be expected as we grow older and unlikely to do much harm, an ever-expanding waistline can increase the risk of many chronic illnesses including some cancers. Scientists believe this may be due to a link between excess body fat and inflammation.

Should I lose weight if I am overweight and have cancer?

The answer to this is, it depends. If you are overweight or have significant abdominal obesity, losing some weight through improving your diet and fitness level will certainly be beneficial. You may even find that if you struggle with weight-related knee or joint pain, losing weight will help alleviate some of this pain.

On the other hand, if you are about to start chemotherapy or radiotherapy, or are struggling with your appetite or ability to eat, you should proceed with caution. It is vital that you get adequate energy and protein intake in order to maintain your muscle mass and strength throughout treatment. Intense dieting is absolutely not recommended, especially during cancer treatment. 

What should I aim for if I am obese?

If you are still not sure, let’s keep it simple.

  1. Aim to improve your fitness level and muscle strength
  2. Aim to improve your eating habits and the quality of your diet
  3. Avoid skipping meals – you need energy and protein and a strong body to help you tolerate your treatment
  4. Lose no more than 0.5kg (1.1lbs) of body weight per week
  5. If you lose weight too quickly, you may start to experience muscle wasting. You may need to eat more foods high in fat and protein to help preserve your muscle mass
  6. Don’t weigh yourself daily or you will drive yourself mad. During treatment, it is common to experience weight fluctuations. This can be due to fluid retention or chemo-related swelling, or changes in your hydration level. Some chemo regimens contain steroids which can increase fatty tissue in the body.
  7. Even without any weight loss, reducing your waist circumference (targets: <88cm for women or <102cm for men) and improving your fitness level will significantly improve your health.

I’ve tried to lose weight in the past, but it never worked. Where do I start?

Before you start, you may need to change your approach. Losing weight requires a whole mindset shift. Instead of adopting a strict ‘must lose weight’ approach, think about adopting new habits, nourishing your body and becoming a healthier version of yourself. There’s a reason that quick-fix weight loss diets and other fads don’t work. They’re extreme and difficult to sustain and can be quite damaging to a person’s sanity and wellbeing.

Quick tips

  • Start small to build confidence. Begin with just one small and simple goal rather than setting yourself up to fail by trying to achieve too much at once. For example: Week 1 – Reduce the sugar in my tea to 50%. Many people make the mistake of setting unrealistic goals which can lead to throwing in the towel early.
  • As the weeks go on you can build on this by adding in new challenges e.g. aim for an extra portion of vegetables with lunch and dinner.
  • Try setting goals Mon-Fri, or every other day, so that the goals are less daunting. This can also be useful for establishing a balanced approach to eating and a healthier relationship with food because it means nothing is off limits.
  • Remember to define why you want to lose weight. If you want something bad enough, you will achieve it! (Marathon runners running for a charity is a good example of this. Nothing will get in their way of the finish line.)


  1. Obesity is having an unhealthy amount or distribution of body fat
  2. Obesity has been linked to some cancers and other chronic disease. This may be due to increased levels of inflammation associated with excess fat
  3. Weight loss, and in particular a reduction to waist circumference, can be beneficial for overall health, reducing the level of fat surrounding internal organs.
  4. We do not recommend rapid weight loss through severe dietary restriction during cancer treatment. This is because it can lead to loss of muscle mass, increasing the risk of treatment-related side-effects and affecting strength and energy levels.
  5. Aim for a gradual weight loss approach through a healthy, nutrient-rich diet combined with plenty of exercise.